Recent years have seen the development of railway cars and roadway trailers which are of extended length relative to the cars and trailers known in the prior art. For example, in rail cars the use of cars well over one hundred feet in length is not uncommon. In railroad applications, the use of longer cars can present difficulties in situations where the car approaches the maximum length which will travel over track sections having the minimum radii of curvature now in use. To account for this, articulated rail cars have been developed which may comprise from two to as many as five or more separate sections which are permanently, flexibly joined to each other. In some types of such cars, each section is independently supported on a single axle truck at each end of the section, thus producing an articulate car which is intended for use as a large, single unit.
Such cars present rather unique problems regarding the type of braking system to be used. The recent U.S. Pat. No. 3,910,641 for Brake System for an Articulated Carrier by Thomas H. Engle, discloses one successful approach to a pneumatically controlled brake system for such a car and also discloses a hydraulically actuated handbrake. In cars where a mechanically actuated handbrake is desired, problems arise which were not addressed in the previously mentioned patent.
The common handbrake linkage used in prior art freight cars comprises a handwheel located on the exterior of the car in a position for manual actuation by a trainman or yard worker. Typically, the hand wheel tensions a chain which actuates a linkage connected to the brake beams, thereby applying the brakes. When the tension is released, the brake beams move away from their applied position due to gravity effects. When this type of linkage is adapted to multiple section, articulated cars of the type previously described, some provision must be made to transmit handbrake force between sections since it is desirable not to have a separate hand wheel for each section, for the sake of simplicity and ease of operation. If flexible connectors such as cables or chains or simple pivoted rods are run between sections to transmit handbrake force, brake application and release become unreliable and spasmodic when the articulated car is negotiating a turn. This is because the linkage in the section with the hand wheel moves toward and away from the linkage in the next section, and so on through the car, as the car turns. The connectors are thus subjected to variable forces so that a partially applied brake in a car section may be fully released or fully applied rather abruptly due to relative motion between sections. Control of the handbrake application or release thus becomes quite difficult when the articulated car is in motion.